The present invention relates to a smart label and a smart label web. The smart label comprises a circuitry pattern on a smart label substrate and a structural part comprising an integrated circuit on a chip on a structural part substrate. The structural part is attached to the smart label substrate and/or the circuitry pattern, and the circuitry pattern is electrically connected to the integrated circuit on the chip. A smart label web comprises smart labels one after another and/or side by side.
Smart labels are often constructed so that sequential and/or parallel circuitry patterns are formed on a flexible web-like substrate and an integrated circuit on a chip is attached to each smart label by a suitable flip-chip technology. Another technique is to attach a separate structural part comprising an integrated circuit on a chip to a smart label. An integrated circuit on a chip is attached by a suitable flip-chip technology to a structural part before attaching the structural part to a smart label. The term flip-chip technology includes many variants, and a suitable technology shall be selected e.g. according to process conditions.
When a chip is attached to a smart label or a structural part by a flip-chip technology, most technologies require a substrate material which must resist high process temperatures. Therefore the selection of materials is limited. Furthermore, when a chip is attached directly on a smart label, the alignment of the chip must be made very accurately. The chip is also very sensitive to mechanical impacts and is easily broken when the bare chip without any cover is processed.
The silicon chips used in smart labels can be quite expensive because they contain a capacitor. At the same time, the capacitor integrated in the chip suffers from inadequate frequency tolerances and poor quality. The design of the circuitry pattern is due the constant inductance restricted. The quality factor of the capacitor in the chip is approximately 80 which does not completely meet the requirements of the whole construction of the smart label. Therefore, the circuitry pattern must be quite thick, which makes the manufacture of the circuitry patterns cumbersome and expensive. Furthermore, the techniques used for forming circuitry patterns are limited. The quality factor refers to the ratio between the stored energy and the energy which is dissipated per cycle. The greater the quality factor is, the smaller is the dissipated energy.
A separate structural part comprising a chip has several advantages but also several deficiencies. The process of attaching the structural part to a smart label substrate is slow and the techniques for attaching are less sophisticated. For example, the structural part must often be placed diagonally with respect the longitudinal direction of the smart label. The structural part may be fastened to the smart label only at its ends by crimping. The crimping makes an electrical connection possible through the substrate of the smart label but then changing stray capacitance may cause harm to the functionality of the smart label because the distance of the structural part from the circuitry pattern varies.
It is possible to attach the structural part substantially entirely on the smart label but it must be attached to the front side of the smart label to provide an electrical contact between the circuitry pattern and the chip. An isolation is required between the structural part and the circuitry pattern which necessitates a separate process step.